1. Field of the Invention
The present invention relates to a method of manufacturing an optical communication module, and a mold and a lead frame suitable for use in the manufacturing method. More particularly, the method enables manufacture of the optical communication module such that a catching part thereof for coupling to a connector is formed at a proper position relative to a distal end of a ferrule.
2. Description of the Related Art
FIG. 6 shows a known surface-mounting optical communication module with a built-in optical communication facility section. The known optical communication module has a structure in which the optical communication facility section is contained in a resin mold 200 having a thin rectangular parallelepiped form, an optical fiber ferrule 142 is projected from one end of the resin mold 200, and a plurality of leads 111 are projected from both lateral surfaces thereof. On the proximal side of the ferrule 142, a catching part 210 is formed for coupling to a connector (not shown) such that the connector is not easily slipped off. The catching part 210 has catching projections 211 formed on its both lateral sides, and the connector has claws engaging with the catching projections 211. When the connector is fitted to the catching part 210, the claws of the connector are brought into engagement with the catching projections 211, whereby slipping-off of the connector is prevented. In order to ensure the positive connection between the optical communication module and the connector, therefore, it is very important to precisely form the catching projections 211, serving as a physical reference position, in a proper position relative to a distal end of the ferrule 142, which serves as an optical reference position.
Such a known optical communication module is manufactured by placing the ferrule 142 and a lead frame 110, on which the optical communication facility section is mounted, in a mold and then filling a resin into the mold so that the optical communication facility section is enclosed and the catching part 210 for coupling to the connector is formed by resin molding.
The method of manufacturing the optical communication module will now be briefly described with reference to FIGS. 7 and 8. First, a light emitting device and/or light receiving device 122 comprising at least one of a light emitting device, such as a photodiode (PD), and a light receiving device, such as a laser diode (LD), is mounted on an Si bench 121 (FIG. 7). On the other hand, a sub-package 100 is prepared on which the Si bench 121 is to be mounted. The sub-package 100 includes the lead frame 110 comprising a mounting part 120 made of an insulating material and a frame portion 130 supporting and insulating the leads 111 from each other. The Si bench 121 and electronic parts 123 are mounted on the mounting part 120. The light emitting device and/or light receiving device 122 and the electronic parts 123 are connected to the leads 111 by wire bonding. An optical fiber capillary 140 is mounted so as to extend from the mounting part 120 to the frame portion 130. The electronic parts 123 used herein include, for example, an LD driver IC, a monitoring photodiode (M-PD) for detecting the intensity of a laser beam emitted from the LD, and an amplifier for amplifying a signal from the PD. The optical fiber capillary 140 is formed by fitting the ferrule 142 to a short-length optical fiber 141. After mounting the Si bench 121, the electronic parts 123, etc. on the sub-package 100, the sub-package 100 is placed on a mold tool and positioned at a proper location within the mold.
The procedures for positioning the sub-package into the mold will be described with reference to FIG. 8. The mold comprises an upper mold tool (not shown) and a lower mold tool 320. A pin and a block positioning projection 360 are formed on an inner surface of the lower mold tool 320. On the other hand, a fitting hole 113 for receiving the positioning projection 360 is formed in a part of the lead frame 110. The sub-package 100 on which the light emitting device and/or light receiving device 122, the electronic parts 123, and the like are mounted is set in the mold such that the positioning projection 360 is fitted to the fitting hole 113. As a result, the position of the lead frame 110 within the mold is determined and hence the position of the distal end of the ferrule 142 mounted on the lead frame 110 is also determined. Then, by closing the mold (i.e., fitting the upper mold tool (not sown) to the lower mold tool 320) and filling a resin therein, a resin molded optical communication module is formed such that the catching part is formed at a desired position relative to the distal end of the ferrule with some degree of accuracy.
However, the above-described related art has a difficulty in forming the catching part with high accuracy at an exactly desired position relative to the distal end of the ferrule by resin molding.
In the conventional resin molding, the catching part for coupling to the connector is positioned relative to the distal end of the ferrule by aligning the positioning projection of the mold with the fitting hole of the lead frame. However, due to part tolerances and variations in accuracy in mounting the ferrule to the sub-package 100, the catching part for coupling to the connector cannot always be precisely positioned relative to the distal end of the ferrule. As a matter of course, various designs, such as forming a positioning groove and providing a positioning attachment, have been proposed for the purpose of precisely mounting the ferrule relative to the lead frame. Those endeavors have failed to eliminate variations in the mounting accuracy to a satisfactory extent.